1. Technical Field
The present invention relates to a head support device to be used in a disk device having a floating-type head, such as a magnetic disk drive, an optical disk drive, or a magneto optical disk drive. The present invention also relates to a disk device having the head support device, and a portable electronic device using the head support device.
2. Background Art
A conventional head support device having a floating-type head of a disk device is described with reference to the accompanying drawings, and a magnetic disk device such as a hard disk device is taken as an example. In FIG. 16, head support device 161 includes suspension 162 having relatively low rigidity, leaf spring 163, and support arm 164 having relatively high rigidity. Suspension 162 has head slider 165 to which a magnetic head (not shown) is mounted on an underside of an end of suspension 162.
Magnetic disk 166 is spun by spindle motor 167. When the disk device reads or writes data, head slider 165 floats above magnetic disk 166 by a predetermined height in response to a balance between floating force and urging force. The floating force is given to head slider 165 due to airflow produced by a spin of disk 166, and the urging force produced by leaf spring 163 of head support device 161 urges head slider toward disk 166. In other words, the magnetic head mounted to head slider 165 floats above disk 166 by the predetermined height.
In reading or writing the data, head support device 161 rotates about bearing 169 due to the activation of voice coil 168 provided to support arm 164. The magnetic head mounted to slider 165 is positioned at a desired track of disk 166 in order to read or write data.
A structure and operation of head support device 161 are described with reference to FIG. 17, which shows a perspective view of an essential part where the magnetic head is mounted to head support device 161. In FIG. 17, the magnetic head (not shown) is provided to head slider 165 placed on the underside of a first end of suspension 162 such that the head confronts magnetic disk 166 (not shown in FIG. 17). A second end of suspension 162 is bent to form leaf spring 163, which is fixed to support arm 164. Leaf spring has cutout section 171 in order to minimize the load variation of head slider 165 to the magnetic disk. This variation is caused by dispersion in the distances between slider 165 and disk 166 when the disk drives are manufactured. Cutout section 171 also helps minimize vertical motion (surface wobbling) of the disk. Leaf spring 163 has a small spring constant so that leaf spring 163 is flexible and has reduced rigidity.
The head support device discussed above is disclosed in, e.g. Japanese Examined Patent Publication Nos. 2894262, 3374846, and Japanese Unexamined Patent Publication Nos. H06-259905, 2004-30856, and 2004-62936.
The foregoing conventional head support device should give leaf spring 163 reaction force strong enough for applying load necessary for head slider 165, to which the magnetic head is mounted, to float over magnetic disk 166 in a stable manner. Leaf spring 163 should be flexible in order to suppress changes in the load applied to disk 166, such changes being produced by the dispersion due to manufacturing.
The reaction force and the flexibility conflict with each other, and in order to satisfy these two conflicting factors, cutout section 171 is formed on leaf spring 163, or suspension 162 is formed by using a thin plate to lower the rigidity of leaf spring 163. Use of a leaf spring having a spring constant small enough to be flexible will lower a resonance frequency when head support device 161 moves the magnetic head to a target track at a high speed, so that a vibration mode such as a twist occurs in head support device 161. As a result, an off-track occurs, and it takes time to clear the invited vibration mode, and these inconveniences have set limits on the progress of shortening the access time.
The conventional head support device has its gravity center at a point nearer to the magnetic head than from leaf spring 163. When an external strong impact is applied to the magnetic disk device, this structure loses the balance between the floating force and the urging force; where the floating force is produced by the airflow at head slider 165 due to the spin of magnetic disk 166 and the urging force urges head slider 165 toward disk 166. The imbalance of these two forces results in an undesirable phenomenon, i.e. head slider 165 jumps from disk 166, or head slider 165 hits disk 166, so that the magnetic head (not shown) and disk 166 can be magnetically or mechanically damaged.
These inconveniences occur not only in the magnetic disk device but also in other disk devices, using a floating-type head, such as optical disk devices and magneto optical disk devices.
On top of that, when an external strong impact is applied to a portable electronic device, to which the foregoing magnetic disk device is mounted, the magnetic head (not shown) or magnetic disk 166 is magnetically or mechanically damaged, so that the electronic device poorly performs its function and invites inconveniences to the actual use.
To overcome these inconveniences, a cushion is prepared before the magnetic disk device is mounted to the portable electronic device, e.g. this structure is disclosed in Japanese Unexamined Patent Publication No. 2004-134036. However, since the portable electronic devices have been downsized recently, it is too hard to mount a cushion strong enough to withstand the external impact into the electronic devices.
Several ideas have been proposed for improving the shock resistance of head support device 161 discussed above. For instance, the head support device with the following structure is proposed: a main portion of the head support device is made from highly rigid material, the head slider is mounted on the underside of a first end of the suspension, and the head support arm is rotatable about the bearing in the radial direction of the magnetic disk, and is also movable vertically on the fulcrum (vertical pivot axis) provided between the head slider and the voice coil placed at the second end of the suspension. The leaf spring for imparting the urging force for generating the load to the head slider is provided to the fulcrum. This structure is disclosed in, e.g. Japanese Examined Patent Publication No. 3374846, Japanese Patent Unexamined Publication Nos. 2004-30856, and 2004-62936.
As discussed above, the head slider floats over the disk due to the balance between the load and the floating force, so that if the balance is lost, the head slider floats in an unstable manner. If an external shock strong enough to cancel the load is applied to the disk device, the head slider is floated only by the floating force, and becomes critically unstable. Suppressing the changes at least in the members other than the head slider pivoting about the vertical pivot axis allows suppressing of changes in the load, so that the head slider can float over the disk steadily. It is thus necessary to set a moving amount less than a predetermined amount; the moving amount is measured from the gravity center position of the respective members except the head slider with respect to the vertical pivot axis.